The present invention pertains generally to threaded fastening systems including a threaded male pin and a female threaded nut. More particularly, the invention pertains to ratcheting fastener systems in which a threaded male pin can be engaged with a threaded female nut by placing a distal end of the pin in the nut and applying axial force to the pin. The invention also pertains to methods of making threaded pins and nuts.
Specialized threaded fasteners are provided for many different uses. In a fastener system often referred to as a ratcheting fastener, a threaded nut and a threaded pin or bolt are adapted to be pushed together for engagement, and rotated as a conventional nut and bolt for disengagement. A ratcheting fastener also can be rotated for engagement, but should resist disengagement from pulling the nut and bolt in opposite directions. Ratcheting fasteners are used on point of purchase displays, and other situations in which relatively rapid setup is desired, and the use of tools is inconvenient. Ratcheting fasteners are also useful and particularly advantageous for attaching components of different thicknesses. A relatively long bolt can be used for attaching both thick and thin components to a display structure by inserting the bolt from the front and pushing the nut onto the bolt from the back. The structures and items being held are wedged snuggly between the head of the bolt and the nut, regardless of thickness so long as the bolt extends completely therethrough with sufficient threads exposed to receive the nut. Commonly, ratcheting fasteners are provided of plastic material, are easy to use and inexpensive.
Known ratcheting fasteners have certain inadequacies and deficiencies. Preferably, the force required to push the nut onto the threaded bolt is substantially less than the pulling force that could result in dislodgement of the nut from the bolt, or failure of the nut or bolt. In practice and design, such features have been difficult to accomplish. If designed and provided for easy xe2x80x9cpush-onxe2x80x9d of the nut onto the bolt, the xe2x80x9cpull-offxe2x80x9d force is also lessened. Thus, a ratcheting fastener provided for easy push-on often can not be used for securing heavy displays and/or bulky items. Conversely, if the ratcheting fastener is designed for increased xe2x80x9cpull-offxe2x80x9d resistance, the xe2x80x9cpush-onxe2x80x9d force required during set-up can make fastening difficult.
Other problems also have been experienced with ratcheting fasteners of known designs. For example, during push-on of the nut, threads in the nut have been broken and/or threads on the bolt have been damaged. In either case, the utility of the fastener is diminished, and disengagement by unscrewing can be made difficult. Further, cross-threading between the nut and bolt can occur, making further engagement or disengagement difficult. Correction of the cross-threading condition often has resulted in thread damage. Additionally, while a low pitch angle for the threads is desirable for fastening, a high pitch angle is desirable for more rapid disassembly. With a high pitch angle, fewer turns are required for removing the nut from the bolt. However, a high pitch angle can result in a loose or sloppy engagement between the nut and the bolt.
What is needed in the art is a ratcheting type fastener system that has a reduced push-on force requirement, with an increased pull-off force resistance, and that resists cross threading and provides rapid disengagement or unscrewing of the nut component from the bolt component thereof.
The present invention provides a ratcheting fastener system including a threaded bolt and a threaded nut received thereon. The bolt and nut are designed for controlled thread deflection to decrease the force required for pushing the nut onto the bolt while retaining a larger force requirement for pulling the nut from the bolt.
The invention provides, in one form thereof, a ratcheting fastener system with a bolt and a nut. The bolt has a shank with a head end and a distal end. A plurality of bolt threads is provided on the shank, each thread having a thread start at the distal end. A nut has a bore, with a plurality of threads in the bore adapted for engaging the bolt threads when axial force is applied to the bolt with the distal end inserted in the nut.
The invention provides, in another form thereof, a nut for a threaded fastener. A nut body has an axial bore and a plurality of thread segments disposed in the axial bore. Each thread segment extends a distance less than a circumference of the axial bore, and has first and second thread segment ends. Ends of adjacent thread segments are spaced from each other in a circumferential direction of the bore. Each thread segment has a thread face and an undercut behind the thread face for providing controlled deflection of the threads.
In a further form thereof, the invention provides a bolt with a shank having a head end and a distal end; a head disposed on the shank at the head end; and a plurality of threads on the shank, each thread having a thread start at the distal end.
In still another form thereof, the invention provides a method of making a fastener, the method having steps of providing a mold having a bolt forming cavity, a nut forming cavity and a connecting link cavity in communication with the bolt forming cavity and the nut forming cavity; and forming a nut and a bolt in the mold, with a frangible link connecting the nut to the bolt. The bolt is formed with a shank having a head end and a distal end, a head on the head end and a plurality of individual threads on the shank each having a thread start at the distal end. The nut is formed with a bore and a plurality of thread segments of substantially equal length and evenly spaced around the bore.
An advantage of the present invention is providing a ratcheting nut and bolt fastener in which the nut can be pushed onto the bolt with a decreased force requirement, while the force required for pulling the nut off the bolt remains high.
Another advantage of the present invention is providing a ratcheting-type fastener with a reduced incidence of thread breaking or thread stripping on either the nut or the bolt.
Yet another advantage of the present invention is providing a ratcheting-type fastener that self-adjusts from a cross-thread condition upon a partial turn of the nut relative to the bolt.
A further advantage of the present invention is providing a ratcheting-type fastener in which the nut fits tightly on the bolt, yet can be removed therefrom with only a few revolutions of the nut on the bolt.
A still further advantage of the present invention is providing a nut and bolt ratcheting fastener manufactured as a single integral component, with the nut and bolt formed of molded plastic and interconnected by a frangible link.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features.